A novel time-of-flight mass spectrometer that utilizes a spiral ion trajectory was developed. In this mass spectrometer, the ions sequentially pass through four toroidal electrostatic sectors and revolve along a figure-eight-shaped orbit on a particular projection plane. Each toroidal electrostatic sector has eight stories, and during multiple revolutions, the ion trajectory shifted perpendicular to the projection plane in every cycle, thereby generating a spiral trajectory. Two prototypes, orthogonal acceleration time-of-flight mass spectrometer (OA-TOFMS) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometer (MALDI-TOFMS) were made and tested. The total flight path lengths were 20 and 17 m for OA-TOFMS and MALDI-TOFMS, respectively. By adopting an ion optical system that has a flight path length more than five times longer than that of the commonly used reflectron ion optical system, the m/z-dependent mass resolving power was reduced while improving the mass accuracy of the mass measurements.